Environmental Impact Assessment Models: Electromagnetic Fields · 2012. 8. 30. · ¾For high...

Egyptian and Italian Cooperation Programme on EnvironmentEnvironmental Impact Assessment (EIA) (for Assessors)

Autore: Mr. Vincenzo Cammarata Mr. Enrico Mazzocchi

“Capacity Building and Strengthening Institutional Arrangement”

Workshop: “Environmental Impact Assessment (EIA) (for Assessors)”

Environmental Impact Assessement Models:

Electromagnetic Fields

Mr. Vincenzo Cammarata, Mr. Enrico Mazzocchi

APAT

Agency for Environmental Protection and Technical Services

22



Environmental Reference Frame Non-Ionizing Radiation

Normative aspects;

Elements for the actual and future characterization;

Impacts assessment



Environmental components and factors definitions by enclose I DPCM 27/12/1988

h)h) Ionizing Ionizing and Nonand Non--IonizingIonizing:: consideredconsidered either either regardingregarding the the natural than natural than the the humanhuman environment; environment;

The The EncloseEnclose II of DPCM 27/12/1988 II of DPCM 27/12/1988 ItIt givesgives the the elementselements for for the the

““CharacterizationCharacterization and and analysisanalysis of the of the componentscomponents and and environmentalenvironmental factorsfactors””



Definitions:Non-Ionizing Radiationsby enclose II DPCM 27/12/1988

The art.5 of the enclose II - D.P.C.M. 27 Dicembre 1988, consider that the environment quality characterization for the Ionizing and Non-Ionizing Radiation component, will have to allow the definition of the trasformation induced by the project, verifying the compatibility with the existing standards and with the prevenction criteria for environment and uman damage, by means of:

a) Medium and maximum radiation level description in the interesting area, for natural and antropic cause, before the project;

b) Sources and emission predictable level definition and characterization in consequence of the project;



Definitions:Non-Ionizing Radiationsby enclose II DPCM 27/12/1988

c) The c) The emittedemitted quantitative quantitative definition definition in in lapse lapse of time and the of time and the final location of the material (final location of the material (keep into keep into account the account the site’s site’s characteristiccharacteristic) in case of the ) in case of the projectproject can produce can produce radioactiveradioactivematerial material relase relase in the environment. in the environment.

d) The d) The predicted level definition predicted level definition in in consequenceconsequence of the of the project forproject forthe the different kind radiationsdifferent kind radiations;;

e) The e) The definition definition of the of the resulting exposingresulting exposing scenario and scenario and their their interpretation interpretation in the light of the in the light of the rilevant reference parameters rilevant reference parameters ((standardsstandards, , acceptability criteriaacceptability criteria, , ectect…);…);

66



Definitions: Non-Ionizing Radiations

by enclose III DPCM 27/12/1988In In particularparticular the the encloseenclose III, in III, in reference reference of of any any class of class of projectsprojects, , specify specify thatthat::

Thermic Thermic station and station and plants for plants for the the electric energyelectric energy production production ((combustion plantscombustion plants, , nuclear nuclear power power plants plants and and other nuclear reactorsother nuclear reactors))Basing Basing of art.5, comma 3, of art.5, comma 3, will have to describe will have to describe and estimate the and estimate the effects effects on on the environment the environment with reference towith reference to the the electric infrastructures electric infrastructures and and electric electric transmission linestransmission lines, , as well as toas well as to the the projectual choiceprojectual choice and and to to the the detecting detecting attenuation mesuresattenuation mesures;;

External aerial electric transmission linesExternal aerial electric transmission lines forfor carrying carrying out and out and distribuition distribuition of the of the electricelectric power power with operational voltagewith operational voltage higher than higher than 150 150 kVkVand and length path higher than length path higher than 15 km.15 km.

77



The The radiation radiation ((electromagnetic waveelectromagnetic wave) can ) can be classifybe classify, in relation , in relation to to the the frequency frequency ad ad energyenergy, as as ““ionizing radiationionizing radiation” or “non” or “non--ionizing radiationionizing radiation (NIR)”(NIR)”

The NonNon--Ionizing RadiationIonizing Radiationbelong to the part of electromagnetic spectrum where the fotonic energy is too much low to break the atomic bond and it basically produce thermical effects.

NIR include: NIR include: Extremely Low Frequency fieldsExtremely Low Frequency fields (ELF, (ELF, fromfrom 0 0 Hz toHz to 10 10 kHzkHz), Radio ), Radio Frequency fieldFrequency field(RF, (RF, fromfrom 10 10 kHzkHz toto 300 300 MHzMHz) e ) e MicroWave fieldsMicroWave fields (MW, (MW, fromfrom 300 300 MHzMHz toto 300 300 GHzGHz))

Impact Evaluation Ionizing and Non-Ionizing Radiation

The Ionizing RadiationsIonizing Radiations,,because their high energy, are able to break the cellular molecular bonds and they can induce genetic mutation.

Extracted picture by PSC Public Service Commition – State of Wisconsin (USA)

The NonNon--Ionizing RadiationIonizing Radiationbelong to the part of electromagnetic spectrum where the fotonic energy is too much low to break the atomic bond and it basically produce thermical effects.

88



For the current-state characterization (before the project realization) the following factors are considered:

Interesting area definition (type of receptors and their description and localization); Location and description of the electrical and physical parameters of sources in the interested project area (frequency, dimensional parameters, electric parameters, etc.);A catalog, with planimetric information, of possible electromagnetic field sources interfering with realizing project (as example electric transmission lines interfering with the railway lines, etc.); Electric, magnetic and electromagnetic field estimation in function of the distance from the source and the surrounding environment characteristic (electromagnetic bottom map before project), Computing algorithm type and version for electromagnetic field estimation (comply with normative CEI).

Current-State CharacterizationNon-Ionizing Radiation

99



Analysis of the Project-Component Interation Non-Ionizing Radiation

The analysis of emitted radiation in the environment following up to project realization, is executed by:

Location and description of the new electrical and physical parameters of sources in the interested project area (frequency, dimensional parameters, electric parameters, etc.); New interesting area definition (type of receptors and their description and localization); Esteem of total radiation levels taking in account of all connectedand not connected sources to the project;Description of adaptation necessary for any interference resolution between sources (like electrical trasmission line) and project;Definition of the mitigation action necessary for the most sensitive and mainly exposed areas;Definition of the post-operam monitoring;



Impact Assessment Non-Ionizing Radiation

The The evaluation evaluation of the of the insertion insertion of the of the projectproject in the environment pass in the environment pass throughtthrought::

Impact Impact predictionprediction, , that is an esteemthat is an esteem of the of the entityentity of the impact of the impact through the through the use use of of numericalnumerical, , logic logic or or other type modelsother type models;;

EvaluationEvaluation of the of the impact’simpact’s entityentity, , that means that means a a evaluation evaluation of of ““quality lossquality loss” of environment in ” of environment in consequence toconsequence to::

-- human resources consumption human resources consumption ((naturalnatural assets, assets, projectsprojects););-- riskrisk of of dangerous situations for human health dangerous situations for human health and and human human

activitiesactivities..

The The evaluation evaluation are facilitate by are facilitate by existing reference standards placeexisting reference standards place by by the the lawlaw..

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Impact AssessmentProperties of electromagnetic fields

The The frequencyfrequency represent a relevant parameter for the physical properties represent a relevant parameter for the physical properties determination of the electromagnetic fields and it indicates howdetermination of the electromagnetic fields and it indicates how many time many time an event repeats in lapse of time. The wave frequency is the numan event repeats in lapse of time. The wave frequency is the number of ber of ripples to the second.ripples to the second.

The The wavelenght wavelenght λλ is is the distance the distance between two consegutive peaksbetween two consegutive peaks of of oscillating waveoscillating wave..c=c=λλ/T or c= /T or c= λλfff =1/T.f =1/T.“c” “c” is is the the speedspeed of light in of light in vacuum vacuum = 300.000 km/s= 300.000 km/sT T is is the the periodperiod

T

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Impact Assessment Properties of electromagnetic fieldsThe The Extremely Low Frequencies electromagnetic fieldsExtremely Low Frequencies electromagnetic fields (ELF) (ELF) havehave similar properties with similar properties with statics fields statics fields (0 (0 HzHz), ), but their amplitude oscillates indipendently withbut their amplitude oscillates indipendently with the time. So the time. So that that are are named named quasiquasi--static fieldsstatic fields..ThereThere are are two quantities that physicists may refer to astwo quantities that physicists may refer to as the the magnetic fieldmagnetic field, , notatednotated H and B. In H and B. In a a vacuumvacuum, , theythey are are equalequal. . AlthoughAlthough the the termterm ""magnetic fieldmagnetic field" " was historically reserved forwas historically reserved for H, H, withwith B B being termedbeing termed the "the "magnetic inductionmagnetic induction“. B “. B is now understood to beis now understood to be the more the more fundamental fundamental entityentity..BB == µµ00H H asas µµ00 vacuum magnetic permeabilityvacuum magnetic permeability. . In SI In SI unitsunits, B and H are , B and H are measuredmeasured in in teslasteslas (T) and (T) and amperesamperes per per metremetre (A/m), (A/m), respectivelyrespectivelyand and it’s trueit’s true the relation: 1the relation: 1 µTµT == 0.80.8 A/m.A/m.For For high high frequenciesfrequencies (RF(RF--MW) the MW) the electromagnetic field may be describedelectromagnetic field may be described in in termsterms of of electromagnetic waveselectromagnetic waves. . Their propagation is associated to energy Their propagation is associated to energy transfer transfer fromfrom the the sourcesource..Electromagnetic radiationElectromagnetic radiation can can be imagined asbe imagined as a selfa self--propagating transverse oscillating wavepropagating transverse oscillating wave of of electricelectric and and magnetic fieldsmagnetic fields. . This diagram showsThis diagram shows a a plane linearly polarised wave propagating plane linearly polarised wave propagating from left to rightfrom left to right. . In the In the vacuumvacuum: E/H = 377 W : E/H = 377 W 377 W (ohm) 377 W (ohm) isis the the impedanceimpedance of the of the vacuumvacuum

..

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Impact Assessment Properties of electromagnetic fields

In the ELF In the ELF rangerange, the , the fields fields E and B take E and B take indipendent valuesindipendent values, so , so it it is necessary tois necessary to estimate estimate both parametersboth parameters to totally defineto totally define the the ““electromagnetic enivornmentelectromagnetic enivornment”.”.

For For RFRF--MW MW radiationradiation, , it is enough to determine it is enough to determine the the electric field electric field or or the the magnetic induction magnetic induction B cause the relation B cause the relation already seenalready seen..

The The mesure mesure of the of the physicalphysical parametersparameters E and B E and B allow to determine allow to determine the the level exposion tolevel exposion to the the electromagnetic fieldelectromagnetic field. So, . So, these these parameters parameters are are named named exposion parametersexposion parameters..

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Near fieldNear fieldShort distance Short distance fromfrom the the source source ((respect to source dimension respect to source dimension and and wavelenghtwavelenght) the ) the electric electric and and magnetic fields have complex distributionmagnetic fields have complex distribution..

ELF (50 ELF (50 HzHz) ) λλ==6000 km6000 kmFar Far fieldfieldFor distances For distances major of major of λλ, the , the electric electric and and magnetic fields have magnetic fields have a regular a regular trend and trend and they travel energy they travel energy far far from from the the sourcesource. . MoreoverMoreover::-- they spread they spread through through spherical wavespherical wave; ; -- they they are are perpendicular each otherperpendicular each other;;-- theythey are in are in spatialspatial and and temporal phasetemporal phase;;-- they have proportional intensitythey have proportional intensity: E =377 : E =377 ··H (in H (in vacuumvacuum or air);or air);-- they they are a single are a single entity named entity named electromagnetic fieldelectromagnetic field. .

Mobile Mobile phonephone (900 (900 MHzMHz) ) λλ=30 cm=30 cm

Impact Assessment Properties of electromagnetic fields

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Impact Assessment Non-Ionizing Radiation

To evaluate electromagneticTo evaluate electromagnetic impact impact is necessary make is necessary make a a distinct analysis respect to distinct analysis respect to the the radiation frequencyradiation frequency..The The two two DPCM (DPCM (Decree Decree of the of the President Council President Council of of MinistersMinisters) 8/07/2003 ) 8/07/2003 that putthat put into into effect effect the the lawlaw 22/02/2001, n°36 22/02/2001, n°36 –– ““Law about protection fromLaw about protection from the the exposures to electricexposures to electric, , magneticmagnetic and and electromagnetic fieldselectromagnetic fields”, ”, regardregard::

DPCM 8/7/’03 DPCM 8/7/’03 -- “Establishment of “Establishment of exposureexposure limits, limits, attention valuesattention values, and , and quality quality goals to protectgoals to protect the the population against electricpopulation against electric, , magneticmagnetic, and , and electromagnetic electromagnetic fields fields at power at power frequencies frequencies (50 (50 HzHz) ) generatedgenerated by power line”by power line”DPCM 8/7/’03 DPCM 8/7/’03 -- “Establishment of “Establishment of exposureexposure limits, limits, attention valuesattention values, and , and quality quality goals to protectgoals to protect the the population against electricpopulation against electric, , magneticmagnetic, and , and electromagnetic electromagnetic fields generatedfields generated at at frequencies betweenfrequencies between 100 100 kHzkHz and 300 and 300 GHzGHz”, ”, for fixed for fixed sourcessources ((fixedfixed telecomunicationtelecomunication and radioand radio--telecomunictiontelecomuniction systemssystems))..For protection against exposure to fieldsFor protection against exposure to fields in the in the frequency rangefrequency range 0 0 HzHz –– 100 100 kHzkHzgeneratedgenerated by by sources unlikesources unlike power power lineslines and and assimilatedassimilated, the , the restrictionsrestrictions set outset outin the EU in the EU RecommendationRecommendation of 12 of 12 JulyJuly 1999 1999 -- publishedpublished in the O.J.E.C. on in the O.J.E.C. on JulyJuly30,1999 30,1999 -- are are appliedapplied in in their entiretytheir entirety..

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Electric field intensity E (V/m) Magnetic Induction B (uT)

Exposure limits5000

(rms values)100

Attention values

10 (median of values recorded over 24 hours under normal

operational condition)

Quality goals

3

DPCM 08/07/2003 “Establishment of “Establishment of exposureexposure limits, limits, attention valuesattention values, and , and quality goals to protectquality goals to protect the the population population against electricagainst electric, , magneticmagnetic, and , and electromagnetic fieldselectromagnetic fields at power at power frequenciesfrequencies (50 (50 HzHz) ) generatedgenerated

by power line”by power line”

(rms values)

(median of values recorded over 24 hours under normal

operational condition)

Quality goal is adopted for the purpose of the progressively minimising exposures to electric and magnetic fields generated by 50-Hz powerlines:a) In designing new power lines in the:- nighbourhood of children’s playgrounds,- residential dwellings,-school premises,-areas where people are staying for-4 hours or more per day,b) In planning developments in the proximity of existing electric power lines and installations, including the categories mentioned above.

Attention value is adopted in children’s playgrounds, residential dwellings, school premises, and in areas where people are staying for 4 hours or more per day. Attention value represent a cautionary measure to protect against any possible long-term effects that might be related to power frequency (50 Hz) magnetic fields.

Exposure limits must not be exceeded

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DPCM 08/07/2003

To determine To determine rightright--ofof--wayway, , reference shall be made toreference shall be made to the the qualityquality goal of Art. 4,goal of Art. 4,and and toto the the electric current loadelectric current load under under normal operating normal operating conditionsconditions of the line, of the line, asasdefineddefined by Standard CEI 11by Standard CEI 11--60.60.

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DPCM 08/07/2003 Art.6 – Parameters to determine right-of-way for power

lines

0

12

Campata a s ingola terna (132 kV ; 100 A )

Z

19 018 017 016 015 0

14 013 012 011010 0

9 08 07 06 0

5 04 03 02 010

Y

171615

14131211109

87

6543

210

X [-20m ;+20m ]

Induzione Magnetica B - Campata a singola terna (132 kV; 100 A)

Distanza [m]

061219253238455158647077839096103116

129141

154167

180193

Altezza [m]

12

11

10

9

8

7

6

5

4

3

2

1

0

X [-50m; 50m]

Edif icio

Picture extracted by simulation software SteMa ver. 1.2 by Euronia

LINE AXESLINE AXES

CAMPO LIMITE ACAMPO LIMITE A 33µµTT

CAMPATA DI 200 m, SINGOLA TERNA 132 kV; 100A

CAMPATA DI 200 m, SINGOLA TERNA 132 kV; 100A

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DPCM 08/07/2003 “Establishment of “Establishment of exposureexposure limits, limits, attention valuesattention values, and , and quality goals to protectquality goals to protect the the population population

against electricagainst electric, , magneticmagnetic, and , and electromagnetic fields generatedelectromagnetic fields generated at at frequencies betweenfrequencies between 100 100 kHzkHzand 300 and 300 GHzGHz””

Exposure limits must not be exceeded

Attention value is adopted in children’s playgrounds, residential dwellings, school premises, and in areas where people are staying for 4 hours or more per day as well as in outdoor annexes that may be used as residential environments, such as balconies, terraces, courtyards, but excluding roof pavings. Attention value represent a cautionary measure to protect against any possible long-term effects that might be related to exposure to fields in the frequency range 100 kHz-300 GHz.valori di CEM che non devono essere superati all’interno di edifici adibiti a permanenze non inferiori a quattro ore giornaliere e loro pertinenze esterne, che siano fruibili come ambienti abitativi quali balconi, terrazzi e cortili esclusi I lastrici solari. Essi costituiscono la misura di cautela ai fini della protezione da possibili effetti di lungo periodo

2020



DPCM 08/07/2003 “Establishment of “Establishment of exposureexposure limits, limits, attention valuesattention values, and , and quality goals to protectquality goals to protect the the population population

against electricagainst electric, , magneticmagnetic, and , and electromagnetic fields generatedelectromagnetic fields generated at at frequencies betweenfrequencies between 100 100 kHzkHzand 300 and 300 GHzGHz””

1. In order to progressively minimise exposure to electromagnetic fields, the calculated or measured values of fields that are the subject of the present decree, shall not, in highly frequented outdoor areas, exceed the values set out in Table 3. The values shall be averaged over any six-minute period in an area equivalent to the vertical cross-section of the human body.2. Highly frequented areas shall include buildings or permanent structures employed for social, health, or recreational needs.

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Impact Assessment The power linesWith With the the term term “power line” “power line” is generally intended is generally intended the set of the the set of the electric trasmission lineselectric trasmission lines, ,

the the trasform substation trasform substation and the and the electrical trasform boothelectrical trasform booth(art.3 L. 22/02/2001, n°36).(art.3 L. 22/02/2001, n°36).

ClassificationClassification of of electric trasmission lineselectric trasmission lines..

TypeVoltage

(kV)Current (A)

Transmission 380 1500Transmission 220 550Primary

distribution150 375

Primary distribution

132

Low voltage distribution

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Electric fieldElectric fieldThe The electric field strenght generated electric field strenght generated

fromfrom power line power line dependsdepends by:by:-- Operating voltageOperating voltage;;-- HeightHeight of power of power wires fromwires from the the

groundground;;-- Conductors geometric configurationConductors geometric configuration

and and their phasestheir phases;;-- Distance Distance from metallic pylon from metallic pylon

structurestructure;;-- LateralLateral distance distance fromfrom the the

longitudinal axis longitudinal axis of the line; of the line; -- Height from Height from the the groundground of the of the

interest interest evaluetedevalueted point;point;

Impact Assessment Electromagnetic characterization of power lines

Magnetic fieldMagnetic fieldThe The magnetic field strenght generated magnetic field strenght generated

fromfrom power line power line dependsdepends by:by:-- Instantaneous currentInstantaneous current in the in the phasephase

conductorsconductors;;-- HeightHeight of power of power wires fromwires from the the

groundground (minimum (minimum heightheight isis indicatedindicatedby DM 449/88 and by DM 449/88 and furtherfurther upup--date date DM 16/01/1991 and 05/08/1998);DM 16/01/1991 and 05/08/1998);

-- Conductors geometric configurationConductors geometric configurationand and their phasestheir phases;;

-- Distance Distance from metallic pylon from metallic pylon structurestructure;;

-- LateralLateral distance distance fromfrom the the longitudinal axis longitudinal axis of the line;of the line;

-- Height fromHeight from the the groundground of the of the interest interest evaluetedevalueted point.point.

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Impact Assessment:Electric field

Figura 3 – Screening effect of a tree on electric field at soil. On x-axes the distance from the line axes.Figura 2 – Lateral profile of the electrical field at 1 m from

ground for typical pylon and voltages.

5

Figura 1 – Lateral profile of the electric field level curves (at 1 m from ground) under a typical power line span at 380 kV double-wire per phase. The vertical axes indicates the distance from the pylon’s axes.

400 m, soil planeE

(kV/m)

UnperturbedUnperturbed fieldfield conditionsconditions The The electric field is strongly prejudiced with electric field is strongly prejudiced with the the presencepresence of of obstacles that essentially obstacles that essentially produce produce two effectstwo effects::

field deformation field deformation ((relevantrelevant in the in the monitoring monitoring because because the the instruments probes instruments probes can alterate can alterate the the local local trend of the trend of the electric fieldelectric field););

Strenght attenuation Strenght attenuation ((screenscreen effecteffect of the of the construction structuresconstruction structures).).

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Pictures extracted from: “Campi elettromagnetici: tecniche di monitoraggio ambientale e principi dell’interazione biologica” di C. Bianchi, A. Lozito, A. Meloni e da simulazioni con il software SteMa ver. 1.2 di Euronia

C a m p a t a a s in g o la t e r n a ( 1 3 2 k V ; 1 0 0 A )

Z

19 01 8 017 016 0

15 014 01 3 012 0

1 1 01 0 09 08 0

7 06 05 04 0

3 02 01 0

Y

1 71 61 5

1 41 31 21 1

1 09

87

6543

21

0

X [ - 2 0 m ; + 2 0 m ]

Impact Assessment Magnetic field

In d u z io n e Ma g n e tic a B - Ca mp a ta a s in g o la te r n a ( 1 3 2 kV ; 1 0 0 A ) Y =1 [m]

Dis ta n z a [m]

0 6 1 2 2 5 3 8 5 1 6 4 7 7 9 0 1 0 31 1 61 2 91 4 11 5 41 6 71 8 01 9 3

B [mic ro T]

2

1

0

X [- 5 0 m; 5 0 m]

The The magnetic field is not significantly magnetic field is not significantly screening screening by by construction structures construction structures and the and the magnetic magnetic induction value remains bond to induction value remains bond to the the current current strenght strenght and and to to the the lineslines distance.distance.

Figura 4 – Lateral profile of the magnetic induction B level curves (at 1 m from ground) under a typical power line span at 380 kV. The vertical axes indicates the distance from the pylon’s axes

Figura 5 – Typical values of magnetic induction B generated by 380 kV, 220 kV, 132 kV, 20 kV power lines under normal operation conditions for different kind of pylons.

CAMPATA SINGOLA TERNA 132 kV; 100A (ad 1 m dal suolo)

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Electric fieldFor electric field estimation exist either analytical model than numerical methods. Between analytical model the best for power line application is that image method based. This method consider:

-Three–phase lines as a set of infinity-lenght conductors;- parallel conductor;- land considered as infinityextension plane.The boundary condition impose a zero potential on plane and than we can substitute the land-plan with charge distribution simmetric and opposite to the plane where the power line lie.

Impact Assessment Previsional model

Magnetic fieldThe magnetic induction B can be calculate as provided for technical norm CEI 211-4, with the method based on Biot.Savart law:

where:ui the infinitesimal lenght of conductor carrying electric current;

ur the unit vector to specify the drection of the vector distance r from the current to the field point.

µ0 I2π d

uIxurB=

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Impact mitigation

Delocalization It consist to detect an alternative path at the entire power line, so to reclaim the major exposed zone.However, in overpopulation zone, it results difficult to realize because the danger is translate on other citizen the problems that have rendered the mitigation necessary.

Move away the power lineIt consist to move away a part of the line. Obviously, in the case of overpopulation, the difficulty is to realize the reclamation cause lack of space.

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Impact mitigationBurrow the line

This solution, usually required by citizens, consist to burrow the cables of the power line. This slution presents any problems:- In case of reclamation zone, an appropriate space is necessary to realize techonological structures that allow the transition from aerial line to burrow cable and vice versa.- High cost for the underground power cables;- High costs for installation and maintenance;- High electromagnetic level produced by burrow line in correspondence of the line.

Figura 6 – Comparison between magnetic induction strenght produced, at the same distance from line axes, by burrow power line and aerial power line when the same currents are flowing. (picture extracted from acts of Conference“Elettrosmog: le ultime novità” organizzato da ANPA e Associazione Ambiente e Lavoro, 2000)

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Impact mitigation

Modification of the phase-conductors geometry in the powerlineThis hypothesis previews to modify the type of the supports to realize a mitigation of the levels of field B taking advantage of the effect that has the position of the conductors in producing actions of compensation of the total magnetic field in the surrounding space. The high-voltage power line is constituted from three conductors whogenerate three magnetic field whose combination produces a reduced totally field, for a compensation and mutual effect. This effect is as well as more obvious as much as the conductors are near.

Pylon n°1 Pylon n° 2 Plyon n° 3

Picture extracted from acts of Conference “Elettrosmog: le ultime novità” organizzato da ANPA e Associazione Ambiente e Lavoro, 2000

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Impact mitigation

From the diagrams we can see that the pylon n°3 that is the “triangle compact support” that has the nearer conductors, introduces inferior valuesof field regarding the others two supports but it has the disadvantage of having a more fragile structure, and it consequently involves limitations on the height of the conductors from earth and smaller length of the catenaries.

Figura 7 – Magnetic induction trend in function of the distance varying the kind of pylon (picture extracted from acts of Conference “Elettrosmog: le ultime novità” organizzato da ANPA e Associazione Ambiente e Lavoro, 2000)

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Height from earth of the phase-conductorThe height of the conductors from earth is an other parameter that is importantin the case of the receptors are near to the power line. Since the catenary possesses a trend with at the center a ventre of minimal distance from the land, in case of the used model does not allow to consider such variability, then the use of the minimal distance of the conductors from the land makes cautelative the esteem carried out with such model.

Impact mitigation

Figura 8 – Magnetic induction trend in function of different height of the conductors (picture extracted from acts of Conference “Elettrosmog: le ultime novità” organizzato da ANPA e Associazione Ambiente e Lavoro, 2000).

Environmental components and factors definitions by enclose I DPCM 27/12/1988

Environmental Impact Assessment Models: Electromagnetic Fields · 2012. 8. 30. · ¾For high...

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Transcript of Environmental Impact Assessment Models: Electromagnetic Fields · 2012. 8. 30. · ¾For high...